Opt-in notifications for threads

[bmos]

Your use case

What would you like to do?

In many messaging clients like Discord, Slack, Mattermost, and others, joining a channel means you get notified of messages in that channel but not in threads within that channel unless you have participated in them. I would like to see this in Element.

Why would you like to do it?

It can be hard to follow everything that is going on in busy rooms, so it's often best not to try. By having opt-in notifications, you can avoid getting pinged by every little thing that's going in in a room.

How would you like to achieve it?

Reacting with emoji, replying in a thread, or reacting to a reply in a thread should subscribe you to the thread. A button should be included in the overflow menu to allow unsubscribing from the thread afterwards.

Have you considered any alternatives?

Having everything on by default and simply allowing muting of threads could be another solution.

Additional context

No response